Such an actuating device is known from U.S. Pat. No. 6,116,325 A. In this case, webs are formed from a flexible material, whereby, with a simultaneous pull on the two strands with a sufficiently great force, the webs are bent apart in such a way that the first partial structure is detached from the second partial structure. With a pull on a single strand, the first partial structure is pivoted in such a way that the first coupling element of a web of the first partial structure comes to rest on a second coupling element of the second partial structure. Consequently, a bending upward of the respective web and thus a detachment of the coupling elements lying on one another is prevented.
The disadvantage in this connection is that an unintentional bending upward of the webs or a detachment of the first and second coupling elements in the locking position cannot be completely ruled out. Further, it is disadvantageous that the webs or the first coupling elements for detaching the first partial structure from the second partial structure have to be bent away from each other. In this connection, there is the risk that the first partial structure is not detached from the second partial structure in a timely manner or only with an unduly great force. Furthermore, the use of flexible or elastic webs may lead to material fatigue and in the worst case to a material rupture. Consequently, there is the risk that the actuating device may not perform its intended function permanently.
Furthermore, it is known that the string element in shading systems with free-hanging string elements, especially when this string element forms a free-hanging loop, must be loosened with a pulling weight of 6 kg or more to meet the DIN standard EN 13120 in order to avoid an injury to a person or a child, especially because of strangulation.